(1) In order to study density fluctuations in the CHS device , a twelve - channel detector array for secondary beams was installed , in which a biasing electrode to suppress secondary electrons emitted from the detector plates due to plasma light was used . However , because of helical magnetic field structure around the detector array , suppression of secondary electrons could not be achieved with a common biasing voltage . Each detector plate should have its own biasing electrode .(2) Dynamic behaviors of plasma potential have been observed in the CHS experiment . This new phenomenon in a toroidal helical plasma is understood as a kind of phase transition caused by nonlinear relation between radial particle flux and radial electric field . The result introduced new insight for plasma physics and magnetic confinement and was presented as invited talks at the International Conference on Plasma Physics ( ICPP98 ) and the International Conference on Plasma Science ( ICOPS98 ) organized by IEEE in US.(3) International collaboration on the heavy ion beam probe for the TJ = II Heliac at CIEMAT , Spain has been proposed and agreed between the two HIBP teams at the National institute for Fusion Science and the Kharkov Institute for Physics and Technology , Ukraine .(4) The HIBP measurements on JIPPT - IIU with multi - channel split - plate detectors demonstrated the power of HIBP for spatial correlation measurement on both density and space potential fluctuations .